Adaptation to submergence
In the Netherlands the river areas are characterized by strongly changing water levels caused by irregular run off of rain and melting water. Flooding in summertime influences the distribution, the population biology and physiological processes of plants in these areas. The zonation of Rumex species seems to be related to this irregular flooding during the growing season as shown in the figure. One of these adaptations is a strong increase in growth of the shoot to restore contact of the leaves with the atmosphere e.g. for uptake of oxygen. The plant hormone ethylene is one of the parameters regulating this growth.
The figure shows Rumex palustris before (right) and after (left) inundation. The submerged plant was able to perform supergrowth to reach the atmosphere. Some of the mystery behind this phenomenon was unraveled by monitoring the internal levels of ethylene inside the plant. These model studies on river plants give general insight in plant behavior in flooding conditions. They are used for understanding optimum adaptation behavior of flooded rice plants and, thus, for rice production.